where to connect component crossover in 97 civic EX? help

I'm very new to this and am replacing the component speakers and the head unit in my 97 civic EX. I've taken the door panel off and this question's about the wiring.

The new tweeter and 6.5" both connect out of the crossover box but in my door panel i can't figure out where to connect the crossover. Do I need to put a new wire from the HU through the door? If so, how? Or can I just connect the crossover to an existing wire inside the door panel?

Thank you, J.